The tree in which we had taken shelter was evidently of great age. I have since heard that some people suppose that the patriarchs of these trees may have been alive before the Flood. The natives cut off and pound the bark, from which they thus obtain the fibres for making a strong and fine cord. Although the bark of many of the trees near their villages is completely torn off in a way that would destroy any other tree, the baobab does not suffer, but throws out a new bark as often as the old one is cut off. Trees are either exogenous--that is to say, grow by means of successive layers on the outside; or they endogenous-- which means that they are increased by layers in the inside. Thus, in the latter, when the hollow is full the growth is stopped, and the tree dies. The first class suffers most severely by any injury affecting the bark; the second, by an injury in the inside. Now the baobab, from possessing all these qualities, may have the bark torn off, and may be completely hollow, and yet continue to flourish. The cause of this is, that each of the lamina possesses a vitality of its own, the sap rising through every part of it. I had seen some trees, from which the natives had so often stripped the bark that the lower part was two or three inches in diameter less than the higher portion which they could not reach. The wood was of a particularly spongy and soft nature; and I was able to cut off enough with my knife to assist in keeping our fire burning. The storm still continued raging without, the wind howling among the branches above our heads, although we sat secure as in a mansion of granite. I was not free, however, from anxiety; for it occurred to me that I might be mistaken as to the tree we were in not attracting the lightning, and that the account I had heard about it might be incorrect. I did not, however, express my misgivings to Natty. He, poor lad, looked very pale and ill, and I regretted having allowed him to walk so far; indeed, I felt it would have been better to have remained at our former abode a couple of days more, or even longer, although it might have made one or more journeys to the fountain necessary. I determined, therefore, to secure the entrance, and make the inside of the tree as comfortable as I could for him, and to remain there till he was better able to proceed.